Long title on gfm doesn't stay in H1

[szimmer]

I have:

• searched the issue tracker for similar issues
• installed the latest version of Quarto CLI
• formatted my issue following the Bug Reports guide

Bug description

If a document has a very long title, the title does not stay in the Header 1 when the output is gfm. Some of it goes on to a new line

Steps to reproduce

````qmd
---
title: "0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789"
format: gfm
---

Oh no my title is too wide for md???
````

Actual behavior

0123456789 0123456789 0123456789 0123456789 0123456789 0123456789

0123456789 0123456789 0123456789 0123456789

Oh no my title is too wide for md???

Expected behavior

0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789

Oh no my title is too wide for md???

Your environment

• IDE: 2025.09.0 Build 387
• OS: Windows 11 x64 (build 22631)

Quarto check output

Quarto 1.8.24
[>] Checking environment information...
      Quarto cache location: C:\Users\sazimmer\AppData\Local\quarto
[>] Checking versions of quarto binary dependencies...
      Pandoc version 3.6.3: OK
      Dart Sass version 1.87.0: OK
      Deno version 2.3.1: OK
      Typst version 0.13.0: OK
[>] Checking versions of quarto dependencies......OK
[>] Checking Quarto installation......OK
      Version: 1.8.24
      Path: C:\Users\sazimmer\AppData\Local\Programs\Quarto\bin
      CodePage: 1252

[>] Checking tools....................OK
      TinyTeX: (external install)
      Chromium: (not installed)

[>] Checking LaTeX....................OK
      Using: TinyTex
      Path: C:\Users\sazimmer\AppData\Roaming\TinyTeX\bin\windows\
      Version: 2025

[>] Checking Chrome Headless....................OK
      Using: Chrome found on system
      Path: C:\Program Files\Google\Chrome\Application\chrome.exe
      Source: Windows Registry

[>] Checking basic markdown render....OK

[>] Checking Python 3 installation....OK
      Version: 3.13.3
      Path: C:/Users/sazimmer/AppData/Local/Programs/Python/Python313/python.exe
      Jupyter: 5.8.1
      Kernels: python3

[>] Checking Jupyter engine render....OK

[>] Checking R installation...........OK
      Version: 4.5.1
      Path: C:/PROGRA~1/R/R-45~1.1
      LibPaths:
        - C:/Users/sazimmer/AppData/Local/R/win-library/4.5
        - C:/Program Files/R/R-4.5.1/library
      knitr: 1.50
      rmarkdown: 2.29

[>] Checking Knitr engine render......OK

[cscheid]

Thanks for the clean repro! Looking into it right now.

[cscheid]

Unfortunately, this is a Pandoc bug:

template.markdown

$if(title)$
# $title$

$endif$
$body$

shell transcript

$ pandoc --version
pandoc 3.7.0.2
Features: +server +lua
Scripting engine: Lua 5.4
User data directory: /Users/cscheid/.local/share/pandoc
Copyright (C) 2006-2024 John MacFarlane. Web: https://pandoc.org
This is free software; see the source for copying conditions. There is no
warranty, not even for merchantability or fitness for a particular purpose.
$ pandoc -t markdown --template=template.markdown issue-13421.qmd
[WARNING] Could not deduce format from file extension .qmd
  Defaulting to markdown
# 0123456789 0123456789 0123456789 0123456789 0123456789 0123456789
0123456789 0123456789 0123456789 0123456789

Oh no my title is too wide for md???

[szimmer]

Argh! I'm not comfortable making a reprex to file an issue with that repro as I don't ever go that deep into pandoc. Is that something the quarto team could do?

[cscheid]

adding --wrap=none works around the problem, but it feels like this shouldn't be needed...

[cscheid]

I started a discussion on the Pandoc board: jgm/pandoc#11166

[cscheid]

There's a way to set nowrap for specific template invocations, TIL. This is just a quarto bug, and will be easy to fix. Thanks for the report!